SYNOPSIS

DESCRIPTION

The
rsautl command can be used to sign, verify, encrypt and decrypt data using the RSA algorithm.

COMMAND OPTIONS

-in filename

This specifies the input filename to read data from or standard input if this option is not specified.

-out filename

specifies the output filename to write to or standard output by default.

-inkey file

the input key file, by default it should be an RSA private key.

-pubin

the input file is an RSA public key.

-certin

the input is a certificate containing an RSA public key.

-sign

sign the input data and output the signed result. This requires and RSA private key.

-verify

verify the input data and output the recovered data.

-encrypt

encrypt the input data using an RSA public key.

-decrypt

decrypt the input data using an RSA private key.

-pkcs, -oaep, -ssl, -raw

the padding to use: PKCS#1 v1.5 (the default), PKCS#1 OAEP, special padding used in SSL v2 backwards compatible handshakes, or no padding, respectively. For signatures, only
-pkcs and
-raw can be used.

-hexdump

hex dump the output data.

-asn1parse

asn1parse the output data, this is useful when combined with the
-verify option.

NOTES

rsautl because it uses the RSA algorithm directly can only be used to sign or verify small pieces of data.

The PKCS#1 block formatting is evident from this. If this was done using encrypt and decrypt the block would have been of type 2 (the second byte) and random padding data visible instead of the 0xff bytes.

It is possible to analyse the signature of certificates using this utility in conjunction with asn1parse. Consider the self signed example in certs/pca-cert.pem . Running asn1parse as follows yields: